CHEMICAL AND ELECTROCHEMICAL-BEHAVIOR OF INDIUM IONS IN THE ZNCL2-2NACL MELT AT 450-DEGREES-C

The stability of indium chloride and oxide as well as the electrochemi cal behaviour of the In3+ and In+ ions have, been studied in the ZnCl2 -2NaCl melt at 450 degrees C by X-ray diffraction (XRD), potentiometry , cyclic voltammetry, chronoamperometry and chronopotentiometry. The s tandard potential of the redox couple In(III)/In(I) and the solubility products of indium oxides have been determined (E degrees In(III)/In( I)= - 1.006 +/- 0.001 V (vs. Cl-2(1 atm)/Cl-), pK(s) = 12.9 +/- 0.2 in molality scale), finding that In(O) is not stable in these mixtures a ccording with the reaction:ZnCl2(dis) + 2In(liq)reversible arrow 2InCl (dis) + Zn(liq) These results have allowed the construction of E-pO(2- ) equilibrium diagrams. Using a tungsten electrode, we observed that t he In(III)/In(I) exchange is quasireversible; log(k(s)(0)/cm s(-1)) an d alpha values for this reaction are (-1.92 +/- 0.09) and (0.51 +/- 0. 06) respectively at 450 degrees C. The average diffusion coefficients D-In(III) and D-In(I) are (5.7 +/- 0.7) x 10(-6), and (6.2 +/- 0.9) x 10(-6) cm(-2) s(-1) respectively.